"This is my version of a winter sock. It has a panel of Nanoseeum at the head that you can turn to a varying degree to vent or even totally enclose you. It is made from ARGON 90 and Nanoseeum so it is breathable but has a quality DWR for quilt protection."
 
The above wording is straight from Dutch and his team. 
 
Ten or Eleven-foot long with a Zip and a choice of colours.